The present invention relates to a ventilator disconnection alarm for use in connection with ventilators such as are used in the practice of medicine to supply air or other gas to a patient incapable of normal breathing.
When a person is paralyzed either by disease or by drugs his life becomes dependent on some form of artificial breathing (called "ventilation") as his own muscles are no longer capable of moving air in and out of his lungs. Generally the breathing machine or "ventilator" is connected to a tube sealed in the patient's trachea and blows gas under positive pressure into the lungs at appropriate intervals. When the inward breath stops the breathing out process is accomplished by the natural collapsing tendency of the lungs independent of muscles or machinery.
As the consequences of prolonged failure of the ventilator or accidental disconnection of the associated tubing are fatal, devices to detect and notify such events are in common use. Powered either by mains or battery these alarms generally detect the rise in back pressure associated with the lung's natural collapsing forces which increase as the lungs fill. If no such pressure rise occurs within a predetermined time an alarm is sounded. Occasionally, without changing the basic principle an alternate event, (such as varying temperature, expiratory flow, or measured expired gas volume) is chosen to detect each breath.
When temporary interference with the breathing equipment is planned or when artificial ventilation is no longer required the alarm is turned off. If, therefore, when ventilation is re-established or another patient connected to the equipment, the attendant is pre-occupied, forgetful, or careless in turning the alarm back on all protection is lost. Some existing devices provide a warning "beep" when temporarily disabled. This warning is not available, however, when power is permanently removed during periods of disuse. Other alarms incorporate a "time-disable" feature whereby the period of disablement is limited to 60 seconds or less. Again such an alarm must be completely shut off when the ventilator is not in use. To eliminate this potential loss of protection against a fatal accident, the present invention provides a new solution.